Rodent Welfare in Laboratories: Improving Conditions for the Most Common Research Animals

Mice and rats comprise the vast majority of laboratory animals globally, and advances in housing, enrichment, and pain management have significantly improved welfare outcomes in research settings.

Key Facts

Mice account for approximately 50-60% of all research animals globally, with rats comprising another 15-20%
Standard laboratory caging for mice has historically provided insufficient space, social housing, and enrichment for their behavioral needs
Nest material provision is one of the simplest welfare improvements — mice spend significant time building and maintaining nests
Social housing of male mice is challenging due to aggression but important for welfare — management approaches have improved
Grimace scales validated for mice and rats allow pain assessment that improves post-procedural pain management
Enriched environments have been shown to improve scientific reproducibility by reducing stress-induced variability in experimental outcomes

Welfare Considerations

Rodent welfare has undergone significant positive transformation in research settings over the past two decades, driven by welfare science research and updated regulatory guidance. Mice and rats are not simple, interchangeable tools — they are social, inquisitive mammals with complex behavioral needs. The provision of nesting material, cage complexity, social housing where possible, and validated pain management has improved welfare outcomes meaningfully. Perhaps most significantly for scientific translation, enriched housing reduces stress-related variation in experimental outcomes, creating a scientific as well as ethical case for welfare improvement. This alignment of welfare and scientific quality is driving sustained improvement.

What You Can Do

Support institutions that exceed regulatory minimums for rodent housing and enrichment
Advocate for regular welfare assessment requirements in laboratory rodent care standards
Support development of further alternatives that reduce rodent research dependence
Learn about the behavioral needs of mice and rats to understand the welfare stakes of laboratory research
Engage with the Three Rs framework as the ethical foundation for continuing improvement in research animal welfare